Stock Spring Rates

[proflex]

This week I was checking the spring rates of some of my spare springs and decided to also check the stock springs out of my 510 just for the hell of it. I thought I would post the results up for any forum members that would maybe like to know the results.
Stock 1972 PL510 2 door {Canadian model}
Front spring rate = 87.5lb/inch ------- Obtained by taking the spring rate after the spring was preloaded to the same height as it would be in the car at its stock ride height.
Rear spring rate = 375lb/inch
Note; springs tested were used stock springs in fair condition {light surface rust, some miles, etc...}.

There are a few different ways of testing spring rates {starting point / preload, etc...} so I have included my test results so people can review the readings and come up with their own conclusions/results. *If this does not interest you there is no need to read any further!!!!!*


Testing method =
Rear spring starting preload was set by compressing the spring down until the starting preload pressure was reached on the spring testers gauge {roughly 1 inch}. It was then compressed 1 inch and the increase on the gauge, over starting preload, would be noted to give the rate of the spring. I also did an additional 1 inch again just to see if I would get an increase close to my last reading.
Rear spring ---1inch = 375lb --------- Rate = 375lb/inch
---------------2 inch = 730lb --------- increase of 355lb
[ If an average of the two readings is used it would work out to a rate of 365lb/inch ]

Being that the front spring is an open ended spring, on both ends{bad for spring rate creep}, I was having problems getting the proper spring rate using the normal preload method. I changed the starting preload by compressing the spring with a spring compressor to near the same height as it would be at ride height in the car and then installed it in the tester and start my readings from there.
Front spring ------- Starting/preload height 9.5
---1 inch = ---75lb increase {spring height 8.5}
---2 inch = --- 80lb increase {spring height 7.5}
---3 inch = --- 95lb increase {spring height 6.5}
The weighted static ride height of the front springs in the car would leave them at around 8 to7.5 inches in height so I averaged the last two readings to get the spring rate.
80lb+95lb / 2 = 87.5lb/inch


Chad

[bertvorgon]

Chad, your pretty much on the money there! Which is why a stock 510 rolls so much . We've come a long way to 300-350 in the front, and 1200 in the back.